L-Amino acids are used in human medicine, in the pharmaceutical industry, in the food industry and very particularly in animal nutrition. It is known that L-amino acids such as, for example, L-lysine, are produced by fermentation of strains of coryneform bacteria, in particular Corynebacterium glutamicum, or of strains of the Enterobacteriaceae family, in particular Escherichia coli. Because of the great economic importance, work is continually being done on improving the production methods. Method improvements may relate to fermentation technology measures such as, for example, stirring and supplying oxygen, or to the composition of the nutrient media, for example the sugar concentration during fermentation, or to the working-up to product form by, for example, ion exchange chromatography or to the intrinsic performance properties of the microorganism itself.
The methods used for improving the performance properties of these microorganisms are those of mutagenesis, selection and choice of mutants. The strains obtained in this way are resistant to anti-metabolites or are auxotrophic for metabolites of regulatory importance, and produce L-amino acids. A known anti-metabolite is the lysine analogue S-(2-aminoethyl)-L-cysteine (AEC).
Methods of recombinant DNA technology have likewise been used for some years for strain improvement of L-amino acid-producing strains of the genus Corynebacterium, in particular Corynebacterium glutamicum, or of the genus Escherichia, in particular Escherichia coli, by modifying, i.e. enhancing or attenuating, individual amino acid biosynthesis genes and investigating the effect on amino acid production.
The nucleotide sequences of the chromosomes of numerous bacteria have been disclosed. The nucleotide sequence of the Corynebacterium glutamicum ATCC13032 genome is described in Ikeda and Nakagawa (Applied Microbiology and Biotechnology 62:99-109 (2003)), in EP 1 108 790 and in Kalinowski et al. (J. Biotechnol. 104(1-3), (2003)). The nucleotide sequence of the Corynebacterium glutamicum R genome is described in Yukawa et al. (Microbiology 153(4):1042-1058 (2007)). The nucleotide sequence of the Corynebacterium efficiens genome is described in Nishio et al. (Genome Research 13(7):1572-1579 (2003)). The nucleotide sequence of the Corynebacterium diphteriae NCTC 13129 genome has been described by Cerdeno-Tarraga et al. (Nucl. Ac. Res. 31 (22):6516-6523 (2003)). The nucleotide sequence of the Corynebacterium jeikeum genome has been described by Tauch et al. (J. Bacteriol. 187(13):4671-4682 (2005)).
A review of various aspects of the fermentative production of L-amino acids can be found in R. Faurie and J. Thommel in Advances in Biochemical Engineering Biotechnology, volume 79 (Springer-Verlag, Berlin, Heidelberg Germany (2003)).
Significant amounts of secreted trehalose are found in the supernatant of industrial fermentations of C. glutamicum. This externally accumulated trehalose is not metabolically recycled by the cells. Said externally accumulated trehalose therefore represents a significant loss in industrial fermentations, both in respect of maximally achievable product formation and with regard to the biomass concentration reached in the fermenter.
Making use of the externally accumulated trehalose is the main goal desired. Achieving this goal would have a plurality of possible positive consequences: (1) utilization of substrate carbon which otherwise remains unused at the end of the fermentation, (2) increase in the biomass achievable in the fermentation, (3) increased product yield in biotechnological production processes, e.g. in amino acid production, (4) avoidance of unwanted contamination in the product supernatant at the end of the fermentation.